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Discussion Starter · #1 ·
I'm wondering if anyone has checked the engine compression. Not sure if you even can on a V-Twin.
I was thinking maybe there is a co-relation to engine compression and horse power.
For example: Lamont said his bike had less HP than Hal's stock. I'm wondering if the engine compression was related.
If so, I would like to find out what good compression is supposed to be on the 109, and what poor compression is.
 

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Uhmmm.. I thought compression was a function of mechanical design of the engine and would only be altered if you changed something like valves, pistons or crank stroke?? :dontknow:
 

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Discussion Starter · #3 ·
You're probably right. However I think older engines loose compression when rings get old etc.
I was thinking each engine might have slightly different compression if each 109 seems to have slightly different Horse Power.
Anyone know?
 

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I don't think any of the 109's are going to have enough miles to start affecting engine compression that much.. least not yet anyway.
 

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interesting you brought that up. I will look in the service manual to see what they do to accomplish that. You see there must be a trick to do it because the 109 has an automatic decompression system to help the poor little starter motor out. when you hit the starter button the engine turns over at a given speed but the decompression devices are on the exhaust cams of both jugs and they hold an exhaust valve open slightly to drop compression. as soon as the motor lights off the speed increases and the decompression devices no longer hold the valves open.
 
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